RIPARIAN METHODOLOGY A Methodology for Defining and Assessing Riparian Areas in the Raritan River Basin New Jersey Water Supply Authority, for the Raritan Basin Watershed Management Project June 2000 METHODOLOGY FOR DEFINING AND ASSESSING RIPARIAN AREAS TABLE OF CONTENTS EXECUTIVE SUMMARY................................................................................................ iii ACKNOWLEDGEMENTS................................................................................................ v 1.0 DEFINITION OF RIPARIAN AREAS ....................................................................1 2.0 ECOLOGICAL FUNCTIONS AND VALUES OF RIPARIAN AREAS....................3 2.1 Wetlands ................................................................................................3 2.2 Wildlife Passage Corridors .....................................................................4 3.0 HYDROLOGICAL FUNCTIONS AND VALUES OF RIPARIAN AREAS...............7 3.1 Floodplains .............................................................................................7 3.2 Steep Slopes ..........................................................................................8 4.0 SOIL DYNAMICS OF RIPARIAN AREAS ............................................................9 5.0 WATER QUALITY/FILTER ZONE FUNCTIONS OF RIPARIAN ZONES ...........10 6.0 BARRIERS AND ALTERATIONS TO STREAM FLOW......................................12 6.1 Dams ....................................................................................................12 6.2 Road Crossings....................................................................................12 6.3 Managed Streams ................................................................................13 7.0 ASSESSING THE HEALTH OF RIPARIAN AREAS...........................................13 8.0 CONCLUSION....................................................................................................16 9.0 LIST OF REFERENCES ....................................................................................17 ii EXECUTIVE SUMMARY Riparian areas that are maintained in their natural state serve a wide variety of functions that help protect streams, lakes, rivers and other waterways from environmental degradation. The destruction of riparian areas and the removal of riparian vegetation for urbanization and development projects can result in the deterioration of aquatic ecosystems and contribute to the impairment of healthy streams and waterways. Stream channels with impaired riparian zones or those entirely without riparian areas do not receive protection from negative influences such as polluted surface water runoff or stream bank erosion. Riparian areas that have been damaged or replaced by impervious surfaces do not provide any benefits to the stream channel or its existing biota. The condition of vegetation along streams is a major component in determining the integrity of riparian ecosystems. In an effort to assess the health and extent of riparian areas that exist within the Raritan River Basin, the New Jersey Water Supply Authority investigated available methodologies to define riparian areas in cooperation with the Raritan Basin Work Group and Project Team. Review of existing scientific literature has shown that no one specific method is practical for defining riparian areas in all areas due to the wide range of existing conditions across the landscape. This report defines riparian areas based on the specific ecological, hydrological, and economical benefits they provide throughout the Basin. Riparian areas will be defined and mapped for the Raritan Basin project using all of the following parameters, with the total riparian area being the sum of the areas defined by the parameters: • Wetlands directly adjacent to stream channels including: o Wetlands larger than one acre o Wetlands modified for agricultural or other purposes (whether such modified wetlands are ultimately included is dependent upon further research) • Wetland transition areas for: o Exceptional resource value (e.g., trout production or fresh water (FW) 1 waters) and intermediate resource value wetlands • Wildlife passage corridors (undergoing scientific peer review) • Floodplains including: o 100-year floodplain o Areas otherwise prone to flooding • Steep slopes (slopes greater than 15%) that are directly adjacent to waterways or to a riparian feature associated with a waterway • All hydric soils that are directly adjacent to surface waters within the Basin • Soils with a seasonal high water table within 1.5 feet of the ground’s surface that are directly adjacent to surface waters within the Basin • Areas along streams that provide shade cover to the streams iii • Specified widths necessary to remove pollutants from surface or ground water flow • Barriers and alterations to stream flow including: o Dams o Road crossings o Managed streams The health of riparian areas will be assessed by determining the extent to which the above areas are no longer in a natural (or fully functional) condition. A conceptual diagram illustrating the approaches detailed in this methodology is presented below. The letters on the diagram represent specific parameters of the riparian area and are described beneath the graphic. A. Trout Stream E. Wetlands Transition Area (150 feet along wetlands of trout production and fresh water (FW) 1 streams; 50 feet along intermediate resource value wetlands) B. Wildlife Passage Corridor F. 100 Year Floodplain (150 feet on each side of all 1st and 2nd Order streams) C. Wildlife Passage Corridor G. Steep Slope (Slopes greater than 15% that flow (300 feet on each side of all directly down to other riparian components of a streams 3rd Order and above) waterway) D. Freshwater Wetlands H. Soils (All hydric, alluvial or soils with a seasonal (Areas 1-acre or larger and high water table within 1.5 feet of the ground’s directly adjacent to streams) surface) iv ACKNOWLEDGEMENTS Primary Author: Deborah J. Newcomb, Watershed Protection Specialist, New Jersey Water Supply Authority Contributing Author: Daniel J. Van Abs, Ph.D., Manager Watershed Protection, New Jersey Water Supply Authority An extended “thank you” to the Raritan Basin Watershed Management Project Characterization Committee and Project Team for all of their comments, hard work and suggestions. Project Team members include: • New Jersey Department of Environmental Protection • New Jersey Water Supply Authority • North Jersey Resource Conservation and Development Council • Rutgers Center for Environmental Communication • South Branch Watershed Association • Stony Brook-Millstone Watershed Association • United States Department of Agriculture – Natural Resources Conservation Service • United States Geological Survey • Upper Raritan Watershed Association v 1.0 DEFINITION OF RIPARIAN AREAS Riparian areas are “complex ecosystems that help provide optimum food and habitat for stream communities as well as aid in the control and mitigation of nonpoint source pollution.”1 Riparian areas facilitate the removal of excess nutrients and sediment from surface water runoff. They shade streams to optimize light and temperature conditions for aquatic plants and animals. Streamside riparian areas have been found to improve the quality of water resources by removing harmful pollutants in storm water runoff and increase the biological diversity and productivity of stream communities.2 Defining riparian areas is a difficult task due to the large number of influencing factors that require consideration, including soil characteristics, hydrology, and landscape features. Riparian areas vary in width, shape, and character and do not stop at any arbitrary, uniform distance away from a stream or watercourse.3 Natural riparian areas are comprised of grasses, trees, or both types of vegetation and can exist within natural, agricultural, forested, suburban, and urban landscapes.4 Based on a review of existing literature, there is no universally accepted definition for riparian areas. Some definitions refer to the term riparian as "the ecosystems adjacent to a river.” According to a scientific literature review on riparian buffers conducted by Seth Wenger of the University of Georgia, riparian areas are defined in two ways: (1) the area along streams and rivers that in its undisturbed state has a floral and faunal community distinct from surrounding upland areas, and (2) the area along streams and rivers which might benefit from some type of protection [including the impact of human land use activities such as farming and construction].5 Riparian areas are often referred to as an “ecotone,” or the boundary that exists between ecosystems. Like many other ecotones, riparian areas are exceptionally rich in biodiversity and exhibit a greater variation in characteristics than either of the systems they connect, which makes them uniquely valuable. Riparian areas perform a wide range of functions with respect to stream health, wildlife uses, and the economic and social values of people. Functions and values of riparian areas include, but are not limited to the following: • Maintaining habitat for fish and other aquatic organisms by moderating water temperatures and providing woody debris; • Storing flood waters, thereby decreasing damage to property; • Stabilizing stream banks and reducing channel erosion; • Offering recreational and educational opportunities; • Providing habitat for terrestrial organisms; • Improving the aesthetics of stream corridors (which can increase property values);